This invention relates to an electrically conducting plastic complex material and, more particularly to such electrically conductive plastic complex material suitably used in a metal-halogen batteries in which metal-halogen is used an active material.
In recent years, the necessity for more effective energy utilization has led to development of a novel type battery making use of metal-halogen as active material. An example of such metal-halogen battery is shown in FIG. 1 which shows in exploded perspective the laminated or stacked structure of the metal-halogen secondary battery through which the electrolyte is circulated.
In FIG. 1, electrodes 1 of the bipolar type and separators 2 are stacked as shown and clamped on both sides by aluminium clamping end plates 11. The stack of these electrodes and separators are united together by bolts 12 and nuts 13. The electrolyte is supplied from a manifold 14 through a channel 15 and a microchannel 19 to the electrode surface and kept in circulation by means not shown. In the drawing, the numeral 16 designates a plastic clamping end plate, the numeral 17 an electrode and plate and the numeral 18 a terminal comprised of a wire net.
The aforementioned metal-halogen battery makes use of monovalent alkali metals such as Li, Na or K or divalent metals such as Zn, Cd, Ni, Co or Fe as metals, Cl, Br or I as halogen and aqueous or nonaqueous solutions as electrolyte. So far, the electrodes comprising a mixture of a synthetic resin material and electrically conductive substances such as metal powders or carbon powders have been used in connection with the aforementioned metal-halogen batteries because these electrodes can be fabricated at lower costs into desired shape because of improved formability of the aforementioned mixture and are excellent in halogen durability. However, these electrodes are defective in that halogen difuse on long period usage from one towards the other side of the electrode, consequently self-discharge occurs and thus loses the function of storage batteries. Thus, when the halogen penetrates through the electrode, problems are caused such that (i) the outer battery casing is damaged by corrosive action; (ii) the energy efficiency of the battery is reduced in proportion to the penetrated halogen; (iii) above all, the bipolar type battery is subject to self-discharge due to halogen penetration; and (iv) the electrode may be degraded by halogen diffusion in the electrolyte.